High frequency radio signaling apparatus



2 Sheets-Sheet l O. S. PUCKLE Filed July 14, 1932 HIGH FREQUENCY RADIOSIGNALING APPARATUS Jan. 2, 1934' Jan. 2, 1934. o. s. PUCKLE 1,941,543HIGH FREQUENCY RADIO SIGNALING APPARATUS 2 Filed July 14, 1932 2Sheets-Sheet 2 WWMWWWWW ..L- 1 Z I INVENTOR 01751 5721/10/06? Pl/C/(ZATTORNEY I Patented Jan. 2, 1934 UNITED STATES PATENT OFFICE HIGHFREQUENCY RADIO SIGNALING APPARATUS Application July 14, 1932, SerialNo. 622,475, and

' Great Britain July 27, 1931 10 Claims.

This invention relates to high frequency transmitters and receivers, andmore particularly to ultra short wave radio transmitters and receivers.I

In short wave radio transmitters and receivers, it is common practice atthe present time to insert choke coils in the energy leads, e. g. frombatteries, to the various points of a transmitter or receiver to whichenergy must be fed, these chokes being provided for the purpose ofpreventing dissipation of radio frequency energy through and from theenergy supply circuits. Such chokes, which ofier very high impedance tothe radio frequency energy, but allow direct currents or low frequencycurrents to pass practically without obstruction, are commonly providedin the filament circuits and in the voltage supply leads to the anodesand grids of the valves in radio apparatus. Where, however, ultra shortwave work is in question i. e. where the working frequency correspondsto a wave length of about 5 or 6 meters or less, and especially wherethe working wave length is below 3 meters, considerable diiiiculty isexperienced in designing and more particularly in testing chokessuitable for thepurpose in question.

The present invention has for its object to provide an easilymanufactured and tested substitute for chokes for use for the purposesabove referred to.

According to' the present invention, instead of using chokes in themanner above indicated, there are employed in substitution for saidchokes, lengths of two conductor line, such lengths being eachapproximately one-quarter of the working wave length or approximately anodd number of quarter wave lengths long and each length of two conductorline is .bridged at or near the end desired, to be of substantially zeropotential at the high frequency by a small terminating load impedance inshunt across the two conductors thereof.

Preferably the two conductor lines consist of lengths of concentricfeeder, the outer tube or conductor of which is maintained substantiallyat earth potential from the point of view of the supply voltage, and theterminating impedance consists of condensers of small impedance.

A two conductor line which is exactly onequarter wave length long and isterminated by a load has an input impedance equal to the square of thecharacteristic impedance divided by the terminating or load impedance.Therefore, by making theload impedance small or the characteristicimpedance large, the input impedance concentric rod or tube, thecharacteristic impedo ance is given by the formula:

Z,,=138 log 10 2-:

where Rz'is the radius of the outer tube and R1 the radius of the innertube or rod. Therefore, by altering the radius of the outer and/or ofthe inner conductor, the characteristic impedance may be varied over awide range.

It will, of course, be appreciated that owing to the presence of thecircuits connected to a two conductor line employed in carrying out thepresent invention, the said line will not in every case be exactly aquarter of a wave length or an odd plurality of quarter wave lengthslong, and it is for this reason that the term approximately" an oddnumber of quarter wave lengths long, has been employed in defining thepresent invention.

Preferablywhere a concentric feeder construction of two conductor lineis employed the said concentric feeder is telescopically arranged sothat its effective length may conveniently be adjusted. If desired also,means may be provided for varying the position of the terminating loadwith respect to the conductors of the two conductor line. Where the twoconductor line is constituted simply by parallel .wires, the terminatingload may conveniently be carried by a simple insulating bridge bridgingthe two wires so that the two terminals of the load are in contacttherewith, the bridge being arranged to be movable along the two wires.Where, however, a length of concentric feeder is employed, it is moreconvenient in practice to arrange the outer conductor in twoparts'sothat it is telescopic. It will be understood. of course, thatfrom the theoretical point of view, adjusting the length of a twoconductor line, for example by employing a telescopic concentric feeder,and adjusting the position of the terminating load are equivalents .ofone another and either or both expedients may be employed as desired.

It is permissible for the conductors of a'two conductor line to extendbeyond the point at which the terminating load is connected, but it isdesirable that the amount of such extension iild not exceed one quarterwave length. For

xample, where the two conductor line is constituted by parallel wires,these wires may extend beyond the bridge carrying the terminating load,while, where a length of concentric feeder is employed, it is convenientto utilize a fixed inner conductor and a telescopic outer conductor andto carry the terminating load from inner or outer of the twoportionswhich together constitute the telescopic outer conductor. Forexample, in one such construction wherein the terminating load isconstituted by a condenser (this construction being suitable for use onvery short wave lengths) one electrode of the terminating load condenseris constituted simply by a small copper or brass tube carried by a discor spider attached to the telescopic outer conductor, the otherelectrode .being the inner conductor. This construction offers theadvantage that, except for the contact between those parts of the outertube which telescope into one another, there are no moving contacts. Asregards this contact between the two portions of the conductor whichtelescope into one another, it is preferable to make the inner of thetwo telescoping portions of thin material (usually copper) so that thechange of impedance at the junction between the telescoping parts iskept as low as possible.

The invention is illustrated in and further explained with reference tothe accompanying drawings.

Referring to Figure 1 which shows the invention as applied to a filamentsupply system, one terminal of the battery or other source 1 isconnected to the central conductor 2 of a concentric feeder 23,one-quarter of a wave length long, and the other is connected to theouter conductor 3, the two conductors 2 and 3 being bridged at the otherend by the filament 4 of the valve 6. The battery end of the feeder 2,3, is also bridged as shown at the appropriate length by a small loadcondenser 5 or other suitable load impedance.

Similarly, in the case of an anode supply system, illustrated in Figure2, the concentric feeder 2, 3, is bridged atone end by the anode cathodespace 4-7 of the valve 6 to be supplied with energy, and at the other bya shunt condenser 5 and in parallel therewith a loop circuit consisting,for example, of the primary 8 of an output transformer 9 and the source10 of anode potential in series. A radio frequency by-pass condenser,not shown, may in certain cases be connected as in the usual way betweenthe anode and filament of the valve 6.

Figure 2a represents the arrangement of Figure 2 schematically redrawnto show the voltage distribution, the said distribution beingrepresented as in the usual conventional manner by means of the brokenline X. Figure 2b corresponds also to Figure 2, but shows the currentdistribution, the said distribution being represented as in the usualconventional manner by the broken line Y. The impedance at that end ofthe concentric conductor indicated by an arrow head in Figures 2a and 2bmay readily be made very large and indeed to approximate to infinity.

A form of concentric feeder suitable for use in carrying out the presentinvention is illustrated in sectional elevation in Figure 3 in which, aswill be seen, the outer conductor consists Tof two parts 3a and 3b whichcan telescope into one another. Figure 4 shows in sectional elevationand Figure 5 in sectional end view, a preferred construction wherein theterminating load impedance is a condenser, this condenser beingconstituted by the central conductor 2 and a tube 5' said conductor andcarried by means of a spider'fi from the part 3a, or the part 3b as maybe desired, of the outer conductor.

The use of telescopic or otherwise adjustable two conductor linespresents, of course, the further advantage of adaptability for efficientuse in receivers which may be desired to operate at any of a pluralityof different wave lengths.

If desired, where telescopic or other adjustable two conductor lines areemployed, a scale and indicator may be associated with the adjustableline, the scale being marked in wave lengths so as to indicate thecorrect adjustment of the length of the line for the different wavelengths marked on the scale, and an insulated handle may be fittedeforcontrol or adjtwtment purposes, e. g. when the apparatus is incorporatedin a radio receiver.

The present invention plicable to push pull and similar symmetricalcircuits. Fig. 6 illustrates such an application. In this circuit theuse of two separate two conductor lines (for example, for use inconnection with feeding anode potential to the two push pull connectedvalves) may in some cases be dispensed with and the two lines becombined in a three conductor arrangement, one conductor beingelectrically and mechanically common to both halves of the push pull orother symmetrical is, of course, also apcircuit. In Fig. 6, whereparallel wires are employed to constitute the two conductor lines theanode feed arrangementfor the pair of valves 15 and 16 in push pullincludes, instead of two separate two conductor lines, an arrangementconsisting of three conductors, 12, 13 and 14 the central conductor 13being common to both halves of the push pull circuit and beingmaintained at substantially earth potential from the radio frequencypoint of view.

In carrying the present invention into practice the smallest possiblenumber of supports or dis tance pieces should be used for locatingtheparallel wires or other conductors of a two wire line or concentricfeeder and such supports or dis+ tance pieces as are employed should, ofcourse, be of good radio frequency insulating properties and lowdielectric loss.

It will be seen that the ,present invention is quite practicable andconvenient and that the device employed in substitution for ordinarychokes is not unduly cumbersome since, in the case of a workingfrequency equivalent to a wave length of 3 meters, the total length of adevice in accordance with this invention would be under 30". If desired,of course, a device in accordance with this invention may be folded.

Although the invention is of general applicaployed in receivers workingon wavelengths of one meter or less, and in circuit'arrang'ementsoperating on the so-called Barkhauseni-Kurz principle or similarprinciple depending upon electronvelocity.

It is to be understood that it is intended to an Odd multiple of a tion,it is, however, very advantageously emtending from said source to theelectrode adapted to be energized, said concentric line comprising anouter conducting tube and an inner conductor insulatingly spaced fromthe walls of said tube and substantially in the center thereof.

2. Apparatus as defined in claim 1 includin "a small load impedanceconnected across said two conductors of said line at the end nearest thesource of potential.

3. High frequency apparatus having, in combination, an electrondischarge device comprising a plurality of electrodes, a source ofpotential for energizing one of said electrodes, a concentric twoconductor line extending from said source to the electrode adapted to beenergized, said concentric line comprising an outer conductingtelescopic tube and an inner conductor spaced from the walls of saidtube and substantially in the center thereof, and a condenserarrangement having a small load impedance across said inner and outerconductors.

4. In high frequency apparatus employing an electron discharge devicehaving a plurality of electrodes and a source of potential forenergizing one of said electrodes, means for preventing the workingfrequency from reaching said source comprising a two conductor lineapproximately an odd multiple of a quarter wave length long extendingfrom said source to the electrode adapted to be energized, said linebeing bridged by a terminating load of small impedance in shunt acrossthe two conductors of said line.

5. In high frequency apparatus employing an electron discharge devicehaving a plurality of electrodes and a source of potential forenergizing one of said electrodes, means for preventing the workingfrequency from reaching said source comprising a two conductor lineapproximately an odd multiple of a quarter wave length long, said linebeing bridged near one end thereof by a terminating load of smallimpedance in shunt across the two conductors of said line.

6. In high frequency apparatus employing an electron discharge devicehaving a plurality of electrodes and a source of potential forenergizing one of said electrodes, means for preventing the workingfrequency from reaching said source comprising an adjustable twoconductor line approximately an odd multiple of a quarter wave lengthlong extending from said source to the electrode adapted to beenergized, said line being bridged near one end thereof by a terminatingload of small impedance in shunt across the two conductors of said line.

7. In high frequency apparatus employing an electron discharge devicehaving a plurality of electrodes and a source of potential forenergizing one of said electrodes, means for preventing the workingfrequency from reaching said source comprising a pair of parallelconductors approximately an odd multiple of a quarter wave length long,said conductors being bridged near the end desired to be ofsubstantially zero potential at the working frequency by a smallterminating load impedance in shunt across the two wires.

8. High frequency apparatus having, in combination, an electrondischarge device comprising a plurality of electrodes, a source ofpotential for energizing one of said electrodes, a concentric twoconductor line approximately equal to an odd multiple of a quarter wavelength long extending from said source to the electrode to be energized,

said concentric line comprising an outer tube and an inner conductorspaced from the walls of said tube and substantially in the centerthereof, and

a terminating load of small impedance in shunt across the two conductorsof said line, said impedance being constituted by a metallic electrodewhich is carried by the outer conductor of said line and which is inelectrostatic association with the inner conductor.

9. High frequency apparatus as defined in claim 8 characterized in this,that said electrode carried by the outer conductor is a tube surroundingthe inner conductor.

10. High frequency apparatus having, in combination, two electrondischarge devices in pushpull relationship each having anode and cathodeelectrodes, said anodes being connected together and said cathodes beingconnected together, a source of potential for said anodes connectedbetween said anodes and cathodes, a three conductor line comprising aninner and two outer conductors, said conductors being parallel for adistance approximately equal to an odd multiple of a quarter wavelength, said inner conductor extending between said cathodes and oneside of

